You may have seen the headlines about CRISPR/Cas9, a powerful genetic technique that lets scientists "edit" genes.

It's been hailed as a miracle method that will cure disease, and also as the nefarious technology that will bring about the era of "designer babies."

CRISPR, which stands for "clustered regularly interspaced short palindromic repeats," is a defense mechanism that evolved in bacteria, but has been adapted for use in many other organisms, including humans. It functions like a genetic "find-and-replace" algorithm, letting scientists go in and edit genes inside living cells.

But how did the technique come about? Here's a timeline of some of the main developments: